This invention relates to vessel turret systems, that is systems that can be used in offshore terminals comprising dedicated vessels, for providing fluid couplings between the vessel and subsea risers/pipelines.
It has been previously proposed to convert a vessel such as an oil tanker into a floating production storage and offloading (FPSO) system by attaching a turret assembly to one end, generally the bow, of the vessel. The turret assembly includes a fluid swivel allowing relative rotation between, firstly, the seabed and associated production risers, mooring chains etc. and, secondly, the vessel itself while maintaining a continuous flow path for production fluids from the subsea well into the vessel. The previously-proposed mounting of the turret assembly has been significantly outboard of the end of the vessel, which has resulted in the turret assembly being exposed to adverse environmental effects, as well as requiring a complex structural mounting arrangement attached to suitable load-bearing portions of the vessel end. Accordingly, once the turret assembly had been fitted, the conversion was effectively permanent, or at least semi-permanent in that considerable work would be required to remove the turret assembly.